A Philippine legislator says he has information that a Chinese surveillance vessel “dropped anchor” more than a month ago in the vicinity of a hotly contested shoal in the South China Sea that the Philippines claims.

Congressman Francisco Acedillo says his intelligence sources learned that the Chinese coast guard vessel was in waters “very near” a dilapidated, rusty old WWII ship, which is lodged onto Second Thomas Shoal.

Fewer than a dozen Philippine soldiers are garrisoned at the grounded BRP Sierra Madre that since 1999 has served as an improvised outpost on the Philippine-claimed shoal.

“To me that presents a very big problem because assuming there is a situation where our marine contingent of eight soldiers is forced to leave Ayungin, that would easily allow the Chinese to gain a foothold in Ayungin Shoal," the lawmaker said.

Acedillo referred to the shoal by its Philippine name, which the Chinese call Ren’ai Reef.

He said the Chinese vessel dropped anchor more than a month ago and it is not immediately clear whether it is still there.

VOA reached out to several military officials to try to confirm Acedillo’s information but authorities did not respond to the inquiries. China has also said nothing about a ship anchored near the shoal.

FILE - An aerial view of one of the structures built by China at the Philippine-claimed Mischief Reef, Spratly Islands in South China Sea.

Worrisome maneuvers

Acedillo, a former Air Force pilot who has closely tracked the progress of China’s artificial-island building projects in the Spratly Islands, says it is even more worrisome that the shoal is just 40 kilometers away from Mischief Reef.

China effectively took control of Mischief from the Philippines in 1995 and is today building out an airstrip and harbor that can accommodate military craft.

China claims just about all of the South China Sea, citing historical data. The Philippines, Vietnam, Malaysia, Taiwan and Brunei also have overlapping claims in the heavily traveled sea abundant with marine life.

Carl Thayer, a Southeast Asia security analyst with the Australian Defense Force Academy of the University of New South Wales, said China anchoring a coast guard vessel in waters near the Philippines outpost likely signifies it is concerned with asserting sovereignty and blocking resupply runs to the ship.

But he said Beijing has to be careful.

“The Sierra Madre is still a commissioned ship of the Philippines Navy and the United States, under the Mutual Defense Treaty, is obligated to consult with the Philippines if the armed forces of the Philippines should suffer an act of force in the Pacific," he noted. "And the commissioned ship with uniformed marines would qualify.”

Thayer says however, that an anchored ship hovering around the shoal still “puts pressure on the Philippines because they never know what to expect next” from China.